I don't understand this line of reasoning. P&G, Unilever, Cocacola, etc have never, not once in history, had a gung-ho C level exec who said "Screw it, I'm going to find out if our advertising works". And then either found it works and kept spending, or found out it doesn't work and saved literally billions of dollars.
There is so much money at stake that could be either saved or generated, its simply not possible that no one has looked at it. I used to help Pepsi/Fritolay set up tracking to tie advertising on youtube to in-store sales. They spent millions of dollars to measure their ads, Google had a clean-room data center specifically for pepsi/frito. The idea that no one actually checked if this system works is simply not possible.
There is so much money at stake that could be either saved or generated, its simply not possible that no one has looked at it. I used to help Pepsi/Fritolay set up tracking to tie advertising on youtube to in-store sales. They spent millions of dollars to measure their ads, Google had a clean-room data center specifically for pepsi/frito. The idea that no one actually checked if this system works is simply not possible.